Viscoelastic properties of dilute macromolecular solutions can provide information about molecular size, shape and flexibility, and polymerization of subunits. The Birnboim-Schrag multiple-lumped resonator will be used to study, at very low concentrations, certain muscle proteins, DNA segments with controlled lengths and nucleotide sequences, and other rodlike biomacromolecules in the frequency range from 100 to 8000 Hz. From the frequency dependence of the storage and loss shear moduli, the rotational relaxation time and the flexural stiffness (expressed for example as a micro-Young's modulus) can be calculated. Studies of the first stage of polymerization of fibrin will be made under various conditions to determine the distributon of oligomers of different sizes and their rates of formation. Measurements of creep and creep recovery on various types of fibrin clots, both ligated and unligated, will be combined with dynamic viscoelastic measurements to follow changes in structure accompanying deformation and recovery. Studies of the elastic and viscoelastic properties of fibrin films will be combined with measurements of small angle and wide angle X-ray scattering to obtain information on the molecular mechanism of elastic deformation and recovery.